A blasting wheel apparatus utilizes centrifugal forces imparted by a driven bladed or vaned "wheel" mounted for rotation within a housing closely enclosing same which housing has a configuration and is so apertured as to define therewith an inlet centrally thereof in the region of the axis of rotation communicating with the internal passageways or channels extending radially outwardly therefrom between the blades and leading to an outlet arranged in generally tangential relation to the bladed wheel periphery whereby the particulate material delivered centrally to the inlet thereof and accelerated under imparted centrifugal forces along the passageways or channels between the blades is discharged from the outlet in a continuous tangentially oriented stream which can be directed against the targeted surface of the component or other article to be treated.
Blasting wheel apparatus of the type under consideration is used in assembly line production where such apparatus may run continuously for several hundreds of hours with the bladed wheel driven between 1800 and 3600 r.p.m.
The particulate material used in those circumstances is highly abrasive and has the effect of wearing away the surfaces of the blades and wheel exposed thereto so that replacement becomes necessary.
The blade surfaces are subjected to greater wear as compared to the exposed surfaces of the wheel in such arrangement and accordingly the blades and supporting wheel are constructed so that they releasably interlock whereby the blades can be replaced when they have become too worn.
The blades for such blasting wheel apparatus are usually cast from abrasion resistant steel and then machined to the desired shape or configuration to achieve longer life. The wheel or disc-like element can either be likewise cast and machined or otherwise derived from suitable metal plate which can then be machined and surface hardened in accordance with known procedures.
It is important however that the upright disposition of blade or vane to the wheel surface be substantially maintained throughout the operational life of the interlocked components so as to promote maximum efficiency and therefore the interconnection between blade and plate should be capable of withstanding deformation or displacement over the aforementioned extended interval of time. Moreover not only should the interlock between blade and wheel be sufficiently strong and durable it also is desirable that engagement and disengagement be readily accomplished so as to minimize downtime.
Accordingly simplicity of form that utilizes a minimum number of components and manipulations yet achieves the requisite strong and durable interconnections and removal for replacement will not only ensure acceptance but contribute as well to efficiency and cost savings in the manufacture of the apparatus.
A number of arrangements for securing the blades or vanes to the wheel have been proposed which are exemplified by the following patents:
U.S. Pat. No. 4,649,673 shows the blades or vanes each attached to the wheel by threaded bolts the heads of which upstand in the respective passageway or channel directly in the path of the accelerating particulate material so that the bolt heads are each subjected to severe wear which may not only weaken the connections and render them unstable but makes each bolt removal and blade or vane replacement difficult as well as time consuming.
The abrasive effects of the bolts becomes the critical factor in scheduling replacement of the blades of the blasting wheel apparatus of U.S. Pat. No. 4,649,673. The bolts generally become abraded more rapidly than the blades themselves, thus requiring replacement before the blades. Accordingly, this blasting wheels apparatus is inefficient as the blades of the blasting wheel apparatus are replaced before such replacement is necessary.
U.S. Pat. No. 3,241,266 reveals blades or vanes each attached to the wheel by a dove-tailed inter-engagement with the wheel presenting machined grooves extending radially and opening to the periphery and the blades or vanes presenting the machined complementary projections which are to be inserted in the grooves or withdrawn therefrom radially from the wheel periphery.
The blades or vanes of U.S. Pat. No. 3,241,266 are adapted to be secured to the wheel by a centrally located removable ring-shaped locking ring and peripherally by inserting wedge type locking pins and incorporate other elements to ensure the requisite interlock to maintain upright disposition of blades or vanes to the wheel surface.
Such complexity of the interlock between blade or vane and wheel make it costly to produce and vulnerable to breakdown as well as difficult and time consuming either when installing or replacing the blades or vanes. Further, the particulate material may work its way in between the blade element and the groove increasing the pressure between the blade element and the groove making the removal of the blade elements from the wheel face difficult and time consuming.
Other U.S. patents of interest include the following:
U.S. Pat. No. 2,582,702 PA1 U.S. Pat. No. 3,162,983 PA1 U.S. Pat. No. 3,160,992 PA1 U.S. Pat. No. 3,197,920 PA1 U.S. Pat. No. 3,287,858 PA1 U.S. Pat. No. 4,333,278 PA1 U.S. Pat. No. 4,402,163 PA1 U.S. Pat. No. 4,473,972 PA1 U.S. Pat. No. 4,480,413